Brush assembly unit



June 4, 1968 D. l. ELOW ET AL 3,387,156

BRUSH ASSEMBLY UNIT Filed June 7, 1963 2 Sheets-Sheet 2 INVENTORS W I ELM LAWRENCE .14 74/5 4 TIMAFXS.

United States Patent 3,387,156 BRUSH ASSEMBLY UNIT David I. Elow, New Rochelle, N.Y., and Lawrence Jayne, Mountain Lakes, N.J., assignors to Consolidated Spring Corporation, Brooklyn, N.Y., a corporation of New York, and to The Carbone Corporation, Boonton, NJ,

a corporation of New Jersey Filed June 7, 1963, Ser. No. 286,246

2 Claims. (Cl. 310-247) This invention relates to current transmitting brush assembly units and components thereof.

An object of the present invention is to provide a greatly simplified spring current transmitting brush assembly unit which is less expensive than present brush assembly units and yet which is comparable in operating performance in that it is capable of transmitting relatively large amounts of current and of withstanding relatively high temperatures without adverse effects on the spring characteristics of the unit.

Another object of the invention is to provide a current transmitting brush unit comprising a conductor and a current-conducting spring member having an element of spring metal to which is bonded an element of electrically conducting material. The spring metal provides the necessary spring biasing force to press the conductor or brush against a rotary commutator or slip ring of a motor or generator, or some other conductor, while the electrically conducting material is effective to transmit the current. Moreover, due to the heat resistance of the spring material, the relatively high temperatures accompanying the current transmission do not adversely affect the spring characteristic of the unit so that good contact of the brush against the conductor, as well as good transmission of large amounts of current, are provided by the unit of the present invention.

Pursuant to another object of the invention, the preferred metal of the spring element is stainless spring steel which is non-magnetic and therefore has no effect on the magnetic fields of the motor or generator which might otherwise be affected with a carbon spring steel. Moreover, the stainless steel element retains its spring characteristics up to 550 F., whereas temperatures above 250 F. adversely affect the spring characteristics of carbon spring steel, due to creep of the material.

A further object is generally to provide an improved brush assembly unit and spring component therefor.

The above and other objects, features and advantages of the invention will be more clearly understood from the following description of the invention considered in connection with the accompanying illustrative drawing in which:

FIG. 1 is a vertical view, partly in section, of a brush assembly unit, in accordance with the invention, mounted in a brush holder therefor;

FIG. 2 is a perspective view of a brush assembly unit, in accordance with another form of the invention, mounted in a brush holder therefor;

FIG. 3 is a perspective view of a brush assembly unit, in accordance with still another form of the invention, mounted in a brush holder therefor;

FIG. 4 is a cross section, on a larger scale, taken on line 44 of FIG. 1;

FIG. 5 is a cross section, on a larger scale, taken on line 55 of FIG. 2;

3,387,156 Patented June 4, 1968 FIG. 5A is a perspective view of a spring member according to another form of the invention;

FIG. 6 is a pers ective view of a brush assembly unit, in accordance with a still further form of the invention, mounted in a brush holder therefor;

FIGS. 7, 8 and 9 are each perspective views of other forms of brush assembly units and holders therefor.

Referring now to the drawing in detail, and first to FIG. 1, the brush assembly unit 10 comprises a current collecting and commutating carbon or graphite brush 12 and a current-conducting spring member 14, herein shown as a helical coil compression spring. The brush is of the usual block form and its outer end is provided with a hub 16 around which the lower convolutions of the spring are coiled in frictional gripping contact therewith. The end 18 of the spring bears against the upper surface 20 of the brush in electrically conducting and spring biasing relation therewith.

The brush assembly unit 10 is mounted in a known type of brush holder 22. The brush holder comprises a hollow plastic body 24 which may be press-fitted into an aperture of the frame 26 of a motor or generator. The upper end of body 24 is internally threaded and is closed by a threaded plastic cap 28. A metal brush and spring guide sleeve 30 is positioned in the body of the holder and extends longitudinally thereof. One end of the sleeve is closed by a wall 32 while its opposite end is open at 34 The opposite end 36 of the spring bears against end wall 32 of the sleeve and is in electrically conducting relation therewith. The brush 12 extends through the opposite open end 34 of the sleeve and is pressed against the commutator 38 of the motor or generator by spring member 14, for electrical contact with the commutator. A terminal member or clip 40 is inserted between the outer side of sleeve 30 and the inner wall 42 of body 24 of the holder, and is in electrical conducting relation with the sleeve. It will be apparent that current is conducted to or from the commutator via brush 12, spring member 14, sleeve 30 and terminal clip 40, and may be transmitted to the field coils of the motor or generator by a lead 44.

In accordance with the invention, as briefly referred to hereinbetore, spring member 14 is a helically coiled wire comprising an element 46 of spring metal to which is bonded an element 48 of electrically conducting metal. As illustrated by FIG. 4, spring member 14 is formed from round wire having an inner coil 46 of spring metal to which is bonded, as by electroplating, an outer coating of electrically conducting metal. The spring metal may be made of stainless spring steel or carbon spring steel, and the electrically conducting metal may be made of copper or aluminum or alloys thereof. It will be understood, as indicated above, that a spring member having a stainless spring steel element is preferred Where the brush assembly unit may be subjected to relatively high temperatures, or where the magnetic field of the motor or generator may be adversely affected by the use of a carbon spring steel element.

- The bonding of the spring element and current conducting element of the spring member may be accomplished by means other than electroplating. For example, the outer coating 48 of spring member 14 may be mechanically bonded to core 46 by passing the wire through a die in lieu of electroplating or in addition thereto.

Moreover, as illustrated by FIG. 5A, the spring member 14 may be a laminated wire having outer layers 48' of electrically conducting metal bonded to an intermedlate layer of spring metal 46', and the bonding may be accomplished by soldering or brazing the layers to each other, or by mechanically joining the layers to each other by applying pressure thereto, as by passing the laminated structure through rollers. Also, with respect to the round wire spring member 14 of FIG. 4, the coating 48 may be bonded to core 46 by hot dipping or by rolling.

It will also be understood that the spring element and conducting element are coextensive in length, and the spring element is less conductive than the conducting element and more resilient than the conducting element.

The inner core spring element 46 of spring member 14 provides the necessary spring properties without being adversely affected by high temperatures while the outer coating 48 of current conducting material provides the necessary current conducting properties for the spring member, and these necessary characteristics are provided with an integral unitary structure. As a result, the spring member is simple and economical to manufacture and makes possible a brush assembly unit having low manufacturing and installation costs, as Well as providing a unit which occupies relatively minor space in relation to the other parts of the motor or generator.

The other figures of the drawing show other forms of the brush assembly unit 10. FIG. 2 illustrates a brush assembly unit a which includes a flat spiral clock-type spring member 14a having one of its ends bearing against the brush 12a in electrical conducting and spring biasing relation therewith. The brush is mounted for sliding movement in the brush holder 22a, which may be mounted on a frame part of the motor, and the brush is biased by the spring 14a against the commutator 38a. The opposite end of the spring is coiled around a terminal member in the form of a metal spring support pin 45, in electrical contact therewith, and lead 44a may be connected to the pin, as shown.

In FIG. 5 the rectangular cross section of spring member 14a is shown and it will be understood that the spring wire is constructed similar to spring member 14 and has an inner core 46a of spring metal and an outer coating thereon of electrically conducting material, as described above.

FIG. 3 illustrates another form of the invention wherein the brush assembly unit 10b includes a torsion spring 14b having one of its ends 46b in electrically conducting and biasing engagement with one end 47 of an electrical conducting metal pivoted arm 48b of a brush holder 22b.

7 The opposite end 50 of the arm is biased against the brush 12b, by the action of the torsion spring, so that the brush contacts the commutator 38b. The brush is mounted for sliding movement in the holder and current is transmitted to or from the brush via arm 48b, torsion spring 14b, and lead 44b which may be connected to a terminal member in the form of a pivot pin support 52 of the spring and arm, it being understood that the other end of the spring (not shown) is electrically connected to pin 52. The structure of the spring wire is as illustrated by FIG. 4 and as described above.

FIG. 6 illustrates another form of brush assembly unit 100 in which the spring member 14c is a spirally wound flat spring of the type wherein the spring force remains constant and is independent of the amount of unwind of the spring. It is to be noted that the coiled end of the spring is biased against the inclined upper surface 200 of the brush 120, in electrically conducting relation therewith, so that the brush is pressed against commutator 38c. The uncoiled end of the spring may be conveniently secured to the holder 220, as by a terminal member or screw 54. A lead 440 may be connected to the uncoiled end of the spring, as shown. The structure of the spring,

In FIGS. 7, 8 and 9, various type of brush assembly units 10d, We and 10 respectively, are illustrated in which the spring members 14d, 14c and 14] are flat leaf springs each being made of flat or strip wire having a structure illustrated by FIGS. 5 or 5A and as described above. In FIG. 7 the spring member 14d is in the form of an inverted U having its arms 56 and 58- in electrical conducting and spring biasing relation with the the top 20d of brush 12d to press the latter against commutator 38d. The cross-bar 60 of the spring bears up against brush holder 22d and a lead 44d is connected to the spring and passes through an opening in the holder.

In FIG. 8 the brushes 12:: are connected to the lower ends of the leaf spring members 14c and are thereby biased against commutator 381:. A lead 44a is connected to the upper end of each leaf spring member as by terminal members or screws 62. The spring may be supported by frame parts 64 of the motor which are insulated from the springs by non-metallic pads 66.

In FIG. 9, the leaf spring member 14 is slightly curved and bears against the top of a brush 12;) to press the latter against commutator 38]. The brush may be mounted for sliding movement in an aperture 68 provided in the frame 26 of the motor. The opposite end of the spring is secured, in insulated relation, to frame 26 by a terminal member or screw 54], and a lead 44 may be secured to the screw internally of the frame.

While we have shown and described preferred embodiments of the invention, it will be understood that the invention may be embodied otherwise than as herein specifically illustrated or described and that certain changes in the form and arrangement of parts and in the specific manner of practicing the invention may be made without departing from the underlying ideas or principles of this invention within the scope of the appended claims.

We claim:

1. A brush assembly unit, comprising a current collecting and commutating brush, and spring means for pressing against said brush, said spring means comprising a wire helical coil compression spring of round outer cross-section, said spring means including a spring metal element and a current-conducting metal element coextensive in length with said spring metal element, said spring metal element being less conductive than said current conducting metal element and more resilient than said currentconducting element, said spring metal element comprising a stainless spring steel inner core of circular crosssection and said current-conducting metal element comprising an outer coating of electroplated metal completely circumscribing the cross-section of the inner core and in contact therewith and being bonded to the inner core, the wire of said spring being drawn, said electroplated metal being selected from the class consisting of copper and aluminum and alloys thereof.

2. In combination, a current-collecting and commutating brush, spring means pressing against said brush, and a conductor in position to be frictionally contacted by said brush as the brush is biased by said spring means, said conductor being movable transversely of the direction in which said brush is biased by said spring means, said spring means comprising a wire helical coil compression spring of round outer cross-section, said spring means including a spring metal element and a current conducting metal element coextensive in length with said spring metal element, said spring metal element being less conductivethan said current-conducting metal element and more resilient than said current-conducting element, said spring metal element comprising a stainless spring steel inner core of circular cross-section and said current-conducting metal element comprising an outer coating of electroplated metal completely circumscr bing the cross-section of the inner core and in contact therewith and being bonded to the inner core, the Wire of said spring being drawn, said electroplated metal being se- 5 6 lected from the class consisting of copper and aluminum 1,679,518 8/1928 Fowle 174-133 and alloys thereof. 2,498,346 2/1950 Smith 310-244 2,695,968 11/1954 Welch 310-246 g g gig gf 2,748,301 5/1956 Spielman 310-240 5 OTHER REFERENCES 670,059 3/1901 Pomeroy 310 244 73 51 5 190 Eek 3 0 4 Product Engmeermg, V01. 31 McGraw-Hlll, New York, 714,811 12/1902 Litchfield 310246 1960, T11 44-41199 1960- 900,730 10/1908 Heath 310244 1 33 34 1921 Beckett 174 3 l0 MILTON 0- HIRSHFIELD, Primary Examine!- 1,580,848 4/ 1926 Newman 310240 L. L. SMITH, Assistant Examiner. 

1. A BRUSH ASSEMBLY UNIT, COMPRISING A CURRENT COLLECTING AND COMMUTATING BRUSH, AND SPRING MEANS FOR PRESSING AGAINST SAID BRUSH, SAID SPRING MEANS COMPRISING A WIRE HELICAL COIL COMPRESSION SPRING OF ROUND OUTER CROSS-SECTION, SAID SPRING MEANS INCLUDING A SPRING METAL ELEMENT AND A CURRENT-CONDUCTING METAL ELEMENT COEXTENSIVE IN LENGTH WITH SAID SPRING METAL ELEMENT, SAID SPRING METAL ELEMENT BEING LESS CONDUCTIVE THAN SAID CURRENT CONDUCTING METAL ELEMENT AND MORE RESILIENT THAN SAID CURRENTCONDUCTING ELEMENT, SAID SPRING METAL ELEMENT COMPRISING A STAINLESS SPRING STEEL INNER CORE OF CIRCULAR CROSSSECTION AND SAID CURRENT-CONDUCTING METAL ELEMENT COMPRISING AN OUTER COATING OF ELECTROPLATED METAL COMPLETELY CIRCUMSCRIBING THE CROSS-SECTION OF THE INNER CORE AND IN CONTACT THEREWITH AND BEING BONDED TO THE INNER CORE, THE WIRE OF SAID SPRING BEING DRAWN, SAID ELECTROPLATED METAL BEING SELECTED FROM THE CLASS CONSISTING OF COPPER AND ALUMINUM AND ALLOYS THEREOF. 